This application claims priority to German patent application no. 199 53 560.4 which was filed on Nov. 3, 1999.
1. Technical Field of the Invention
The invention relates to a circuit breaker having a contact tube which is hollow in order to carry away hot switching gases and bounds the breaker gap, and whose outlet opening interacts with a stationary guide body which is arranged at a distance from it.
2. Background of the Invention
A circuit breaker is described, for example, from Laid-Open Specification DE 39 04 439 A1. In the known arrangement, which is intended by way of example for 145 kV, the hot switching gases which are produced in an arc in the breaker gap during a disconnection process are carried away through the interior of a stationary contact tube. In this case, the hot switching gases are passed out of an outlet opening of the contact tube to a stationary guide body. In the known arrangement, the contact tube is arranged such that it is stationary, so that the distance between the outlet opening and the guide body always remains the same, resulting in a constant, guided gas flow.
In order to achieve better dielectric strength for the breaker gap in the circuit breaker, it is desirable for the distance between the contact which bound the breaker gap to be made as large as possible during the disconnection process. In the known arrangement, the separating gap can be enlarged during the disconnection process only by lengthening the operating travel of the moving contact.
The present invention discloses, in one embodiment, a circuit breaker such that the separating gap is enlarged in the disconnected position without lengthening the operating travel of the moving contact, and without adversely affecting the way in which the hot switching gases are carried away.
In one aspect of the invention, a contact tube is guided such that it can move axially, and the outlet opening is surrounded by a stationary nozzle-shaped flow guide in every position of the contact tube during the movement.
The capability of the contact tube to move axially makes it possible, in a simple manner, to enlarge the separating gap in the circuit breaker in the disconnected position, with the stationary flow guide guiding the flow of hot switching gases independently of the position of the contact tube, and hence independently of its outlet opening. The guide body and the nozzle-shaped flow guide are separated from one another by the same distance. It is thus possible in conjunction with the guide body and the flow guide to ensure that the same boundary conditions are provided for the flow of switching gases.
It is advantageously possible to provide for the flow guide to be composed at least partially of an insulating material.
A further advantageous embodiment provides for the guide body to be composed at least partially of an insulating material.
If the flow guide and the guide body, or one of the two, is at least partially comprised of a suitable insulating material, then it is possible to reduce the electrical conductivity of the hot switching gases as well, if, for example, PTFE is chosen, which releases electrically negative gas components under the influence of hot switching gases. The flow guide and guide body may be formed from a number of parts. In this case, it is possible for the individual pieces to be composed of different materials.